Short Term Workers and the Risk of Lung Cancer and

Comparing and contrasting short term workers with their long term colleagues provides some interesting data regarding risk of cancer and mesothelioma. One interesting study is called, Mortality of workers employed in two asbestos cement manufacturing plants by J. M. Hughes, H. Weill, and Y. Y. Hammad - Br J Ind Med 1987;44:161-174. Here is an excerpt: Abstract - In a study of the mortality experience of 6931 employees of two New Orleans asbestos cement products manufacturing plants over 95% were traced. Chrysotile was the primary fibre used in both plants. Plant 1 also used small amounts of amosite and, later, crocidolite irregularly whereas plant 2 used crocidolite steadily in pipe production. Previously reported exposure concentration estimates were revised, based on additional air sampling data and re-evaluation of these data. Workers in the two plants had similar duration of employment (overall, a mean of 3.8 years) and estimated exposure concentration (a mean of 7.6 million particles per cubic foot (mppcf)).

Mortality was similar for these plants and comparable with Louisiana rates for all causes combined, nonmalignant causes, and primary cancers of specified sites other than lung. Short term workers from both plants showed raised and similar risk of lung cancer, but risk among longer term workers differed--for example, for workers employed over one year there was no excess in plant 1 (16 observed, 17.2 expected) but a significant excess in plant 2 (52 observed, 28.9 expected, p less than 0.001). After excluding short term workers, risk of lung cancer in plant 2 showed a significant trend with estimated cumulative asbestos exposure; using a conversion of 1.4 fibres/ml = 1 mppcf, the slope of the line was 0.0076. The slope for plant 1 was 0.0003. Among all workers (the 6931, plus 167 early employees) ten mesotheliomas had occurred up to 1984: two from plant 1, eight from plant 2. In plant 2 a case-control analysis found a relation between risk of mesothelioma and duration of employment (p less than 0.01) and proportion of time spent in the pipe area (p less than 0.01), thus adding to the evidence of a greater risk of mesothelioma from crocidolite than chrysotile asbestos. A review of the mortality findings of eight cohorts of asbestos cement workers is presented.

Another interesting study is called, Benign asbestos pleural effusion: 73 exudates in 60 patients by Hillerdal G, and Ozesmi M. - Eur J Respir Dis. 1987 Aug;71(2):113-21. Here is an excerpt: All patients seen in 1975 to 1984 with benign asbestos pleural effusion (BAPE) were studied. In all, 73 exudates occurred in 60 patients, 40 on the left side and 33 on the right. Relapses occurred on the same side in two patients; 11 had bilateral exudates, three of them concomitantly, in the other patients with a free interval of 1-15 years. The mean latency time from the first exposure to asbestos was 30 years, with a range of 1 to 58 years. The effusions lasted from 1 to 10 months, with a median of 3 months. The most common symptoms were pain, fever, cough, and/or dyspnoea; however, 46% of the episodes were symptomless. The total number of thoracocenteses was 66, with removal of 50 to 2000 ml (mean 460) each time. Fifty-three per cent of the pleural fluids were macroscopically haemorrhagic and 26% eosinophilic. Two findings contribute to a better understanding of the entity: first, even a comparatively slight occupational exposure can be sufficient; secondly, BAPE can occur many years after exposure to asbestos, and not only in the first one or two decades.

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